A phase difference plate is widely used as a component of a display device such as a liquid crystal display device and an organic electroluminescent display device. Hereinafter, organic electroluminescence may be referred to as “organic EL”. A phase difference plate used in the display device may be required to uniformly express a desired retardation of ¼ wavelength, ½ wavelength, or the like in the entire wavelength region for displaying (usually visible region), thereby exerting the effect in the entire wavelength region for displaying.
As one of methods for producing such a phase difference plate, there is known a method of molding a compound capable of exhibiting a liquid crystal phase into a solid film while the liquid crystal phase is kept. Examples of the method may include a method in which a composition containing a polymerizable liquid crystal compound that is polymerizable and is capable of exhibiting a liquid crystal phase is applied onto a surface of an appropriate substrate to form a layer, and the polymerizable liquid crystal compound in the layer is oriented, and then polymerized while the oriented state is maintained, to form a film having an optical anisotropy. According to this method, a phase difference plate that uniformly expresses a retardation in the plane can be obtained. Further, when the polymerizable liquid crystal compound is appropriately selected, a phase difference plate that expresses a uniform retardation in a visible light wavelength region can be obtained with this method. As a method for orienting a compound capable of exhibiting a liquid crystal phase in this method, various methods have been investigated in prior art. For example, a method for orienting a liquid crystal compound using a film that has been subjected to stretcing treatment as a substrate has been known as those in Patent Literatures 1 to 3.